From a57e06c3dd1a01d00dfd016ae900ba861b39b2e8 Mon Sep 17 00:00:00 2001
From: Andrei Ovcharenko <a@krot.name>
Date: Fri, 31 Jul 2026 17:39:23 +0300
Subject: [PATCH] Validate sprint8 CLI input

---
 src/main/java/algorithms/sprint8/Crib.java    | 32 ++++++++-
 .../java/algorithms/sprint8/PackedPrefix.java | 65 ++++++++++++++++++-
 2 files changed, 94 insertions(+), 3 deletions(-)

diff --git a/src/main/java/algorithms/sprint8/Crib.java b/src/main/java/algorithms/sprint8/Crib.java
index 18d15d2..c8f665b 100644
--- a/src/main/java/algorithms/sprint8/Crib.java
+++ b/src/main/java/algorithms/sprint8/Crib.java
@@ -35,12 +35,22 @@
 public class Crib {
 
     static boolean solve(String text, String[] words) {
-        int totalLength = 0;
+        if (!isLowercaseWord(text)) {
+            return false;
+        }
+
+        long totalLength = 0;
         for (String word : words) {
+            if (!isLowercaseWord(word)) {
+                return false;
+            }
             totalLength += word.length();
+            if (totalLength >= Integer.MAX_VALUE) {
+                return false;
+            }
         }
 
-        Trie trie = new Trie(totalLength + 1);
+        Trie trie = new Trie((int) totalLength + 1);
         for (String word : words) {
             trie.add(word);
         }
@@ -76,6 +86,17 @@ static boolean solve(String text, String[] words) {
         return dp[chars.length];
     }
 
+    private static boolean isLowercaseWord(String word) {
+        for (int i = 0; i < word.length(); i++) {
+            char current = word.charAt(i);
+            if (current < 'a' || current > 'z') {
+                return false;
+            }
+        }
+
+        return true;
+    }
+
     static final class Trie {
         final int[][] next;
         final boolean[] terminal;
@@ -207,6 +228,13 @@ private static void run() throws Exception {
 
         String text = in.next();
         int n = in.nextInt();
+        if (n < 0) {
+            out.writeString("NO");
+            out.writeByte('\n');
+            out.flush();
+            return;
+        }
+
         String[] words = new String[n];
 
         for (int i = 0; i < n; i++) {
diff --git a/src/main/java/algorithms/sprint8/PackedPrefix.java b/src/main/java/algorithms/sprint8/PackedPrefix.java
index 66c2420..859ab05 100644
--- a/src/main/java/algorithms/sprint8/PackedPrefix.java
+++ b/src/main/java/algorithms/sprint8/PackedPrefix.java
@@ -40,6 +40,10 @@ public class PackedPrefix {
     private static final int MAX_UNPACKED_LENGTH = 100_000;
 
     static String solve(String[] packedStrings) {
+        if (packedStrings.length == 0 || !isValidPacked(packedStrings[0])) {
+            return "";
+        }
+
         String first = decodePrefix(packedStrings[0], MAX_UNPACKED_LENGTH);
         int prefixLength = first.length();
 
@@ -47,6 +51,9 @@ static String solve(String[] packedStrings) {
             if (prefixLength == 0) {
                 break;
             }
+            if (!isValidPacked(packedStrings[i])) {
+                return "";
+            }
             prefixLength = commonPrefixWithPacked(packedStrings[i], first, prefixLength);
         }
 
@@ -234,6 +241,45 @@ private static int[] buildMatchingBrackets(String packed) {
         return matchingBracket;
     }
 
+    private static boolean isValidPacked(String packed) {
+        int top = 0;
+
+        for (int i = 0; i < packed.length(); i++) {
+            char current = packed.charAt(i);
+
+            if (current >= 'a' && current <= 'z') {
+                continue;
+            }
+
+            if (current >= '0' && current <= '9') {
+                if (i + 1 >= packed.length() || packed.charAt(i + 1) != '[') {
+                    return false;
+                }
+                continue;
+            }
+
+            if (current == '[') {
+                if (i == 0 || packed.charAt(i - 1) < '0' || packed.charAt(i - 1) > '9') {
+                    return false;
+                }
+                top++;
+                continue;
+            }
+
+            if (current == ']') {
+                if (top == 0) {
+                    return false;
+                }
+                top--;
+                continue;
+            }
+
+            return false;
+        }
+
+        return top == 0;
+    }
+
     // -------------------- FAST INPUT --------------------
     static final class FastIn {
         private final InputStream in;
@@ -357,7 +403,20 @@ private static void run() throws Exception {
         FastOut out = new FastOut(System.out);
 
         int n = in.nextInt();
-        String first = decodePrefix(in.next(), MAX_UNPACKED_LENGTH);
+        if (n <= 0) {
+            out.writeByte('\n');
+            out.flush();
+            return;
+        }
+
+        String packedFirst = in.next();
+        if (!isValidPacked(packedFirst)) {
+            out.writeByte('\n');
+            out.flush();
+            return;
+        }
+
+        String first = decodePrefix(packedFirst, MAX_UNPACKED_LENGTH);
         int prefixLength = first.length();
 
         for (int i = 1; i < n; i++) {
@@ -366,6 +425,10 @@ private static void run() throws Exception {
             }
 
             String packed = in.next();
+            if (!isValidPacked(packed)) {
+                prefixLength = 0;
+                break;
+            }
             prefixLength = commonPrefixWithPacked(packed, first, prefixLength);
         }